The present invention relates broadly to orifice piston expansion devices for metering the flow of a refrigerant along two or more fluid flow paths within a refrigeration system such as between the condenser and evaporator coils of a heat pump or other reversible refrigeration cycle, and more particularly to a universal body for such device which is adapted to be interchangeable with existing pistons of a 3- or 5-fluted, gasketed variety, or of a double headed variety.
Air conditioning and other refrigeration systems are operated in a thermodynamic cycle which conventionally employs in series, as is shown at 10 in FIG. 1, a compressor, 12, a first heat exchanger or condenser, 14, an expansion function, represented at 16, and a second heat exchanger or evaporator, 18, all of which are arranged in a closed-loop circuit. Within such circuit 10, a refrigerant medium is cycled therethrough for its alternate conversion from a partially liquid to a partially gaseous state effecting a concomitant loss of heat.
When operated in a conventional cooling mode, energy is supplied into the thermodynamic cycle via the compressor 12 which is operated as having a low pressure inlet or suction side, 20, and a high pressure outlet or discharge side, 22. Within the compressor, the refrigerant is compressed and super-heated to exit the outlet side 22 thereof at a relatively high pressure. The refrigerant next is passed through the first heat exchanger 14 wherein a heat transfer is effected with a lower temperature fluid to remove the heat of compression from the refrigerant for its further cooling. From the first heat exchanger 14, the flow of the refrigerant, which is now in a liquefied and pressurized state, is regulated by the expansion function 16 and then is passed into the second heat exchanger 18. The refrigerant within the second heat exchanger 18 is volumetrically expanded with a state change from a high to a low pressure liquid, and subsequently a phase change to a low pressure gas. The specific and latent heats associated with the state and phase changes of the refrigerant effect the cooling of the area surrounding the second heat exchanger 18 or, with forced convective systems, of a higher temperature cooling medium such as air which is circulated in a heat transfer relationship with the heat exchanger. From the second heat exchanger 18, the refrigerant, now in a relatively low pressure gaseous phase, is returned to the suction side 20 of the compressor 12 wherein it is again compressed and thereafter cooled for the repetition of the cycle.
However, and as is detailed in U.S. Pat. Nos. 3,992,898 and 5,341,656, refrigeration systems of the above-described type also may be operated in an alternate thermodynamic or "heat pump" cycle to additionally heat the working environment. When operated in such mode, the duty of the two heat exchangers typically is reversed thermodynamically by physically reversing the direction of the flow of refrigerant through the system. In this regard, and as is shown at 30 in FIG. 1, a multi-position valve may be coupled in fluid communication with the suction and discharge sides of the compressor to selectively connect the heat exchangers to alternate sides of the compressor such that the first heat exchanger may be operated in a cooling or evaporator mode, with the second heat exchanger being operated in a heating or condenser mode.
As will be appreciated, to complete the thermodynamic reversal of the cycle, the refrigerant within circuit 10 must be throttled in the opposite direction through the expansion device. Therefore, the expansion function of such circuits conventionally may employ a double expansion device arrangement wherein a pair of expansion devices, referenced in FIG. 1 at 16a-b, are positioned in opposition within the supply line, 32, extending between heat exchangers 14 and 18. That is, devices 16a-b are arranged to throttle refrigerant in opposite directions. Expansion devices, which encompass capillary tubes, thermostatic expansions valves, and orifice piston-operated check valves, are further described in U.S. Pat. Nos. 5,695,225; 5,564,754; 5,553,902; 5,341,656; 5,131,695; 4,674,673; 4,643,222; 3,992,898; 3,877,248; 3,745,787; 3,120,743; and D341,409. Further, it is common practice to distribute the refrigerant discharged from each of the expansion devices 16 into a plurality of different circuit tubes, one of which is referenced at 34a for device 16a, and at 34b for device 16b, each of which is connected to a different section of the corresponding heat exchanger coil.
As is detailed in U.S. Pat. Nos. 3,992,898 and 5,341,656, a representative orifice piston expansion device of a "doubled headed" piston variety comprises an, elongate housing including a generally cylindrical internal chamber which extends intermediate a forward and a rearward end. The forward end terminates at axially rearwardly-facing raised ring which defines a generally annular, flat seating surface. The second end, in turn, terminates at a generally annular stop surface which may be presented from the leading edge of the forward or flange end of a union-type adapter. The other, rearward end of the adapter may be configured for a sweat or other connection with the interconnecting supply line which couples the paired expansion devices. Accordingly, in the circuit arrangement illustrated in FIG. 1, the forward chamber end may be coupled in fluid communication with the corresponding coil, with the rearward chamber end being coupled in fluid communication with the other expansion device.
A free-floating piston is received within the housing chamber to be slidably movable responsive to the direction of fluid flow from a first position disposed at the forward end of the chamber, to a second position disposed at the rearward end of the chamber. The piston, which extends intermediate truncated frusto-conical first end disposed confronting the forward chamber end and a truncated frusto-conical second end disposed confronting the rearward chamber end, is specially constructed as having a centrally-disposed, axial throughbore. The throughbore functions as a metering orifice to throttle refrigerant flowing into the corresponding coil. The piston further is formed a having an enlarged diameter boss portion extending intermediate the first and second ends thereof. The boss portion has a forward end defining a generally annular sealing surface configured for an abutting, fluid-tight engagement with the seating surface of the forward chamber end, and a rearward end. The boss portion is further configured to define a plurality of spaced-apart fins, each having a pair of opposing lateral surfaces and extending radially-outwardly from the boss portion. Each of the fins further extends axially along the boss portion from a forward end to a rearward end which is abuttingly engagable with the stop surface disposed at the rearward chamber end for delimiting the travel of the piston in the rearward direction. The lateral surfaces of the fins each defines a peripheral fluid passageway with an opposing lateral surface of an adjacent fin and the interior surface of the chamber.
In operation, with refrigerant flowing in a forward direction through the device, the piston is advanced responsive to fluid pressure to a first position wherein the boss seating surface is disposed in abutting, fluid-tight contact with the chamber seating surface. With the piston being disposed in such first position, the entirety of the refrigerant flow is throttled through the metering orifice. When the refrigerant flow is reversed, the piston is advanced responsive to reverse fluid pressure to a second position wherein the rearward ends of the fins are disposed in an abutting engagement with the chamber stop surface. With the piston being disposed in such first position, a lower pressure drop refrigerant flow is vented through the peripheral passageways.
Representative orifice piston expansion devices of a gasketed piston variety are detailed in U.S. Pat. Nos. 5,695,225; 5,564,754; and 4,643,222. Such devices operate similarly to the double headed piston devices described hereinbefore, with the exception that in the first or forward position of the piston, the fluid tight seal between the piston forward end and the chamber seating surface is effected by way of a compressible seal ring. In this regard, an annular groove or gland is integrally-formed about the forward end of the piston. The gland is configured to receive an o-ring, rectangular cross-section, or other gasket seal which may be formed of a fluoropolymer material such as polytetrafluoroethylene (PTFE) or a synthetic rubber material such as a neoprene. The seal is mounted within the gland such that a forwardly-presented axial surface thereof defines the sealing surface of the piston for abutting contact with the chamber seating surface. Gasketed piston are commercially provided as having either 3 or 5 fins and a to define a corresponding number of peripheral passageways or "fluted" channels.
Orifice pistons of the above-described double headed and gasketed varieties are manufactured commercially by the Byron Manufacturing Division of Parker-Hannifin Corporation (Siloam Springs, Ariz.), by Chatleff Controls, Inc. (Buda, Tex.), and by Spinco Metal Products, Inc. (Newark, N.J.). Refrigeration system manufacturers include Carrier Corporation (Syracuse, N.Y.), Rheem Manufacturing Co. (Fort Smith, Ariz.), and Trane Co. (La Crosse, Wis).
With respect to component manufacturers, the type and configuration of the expansion device, whether as original equipment or for replacement parts, typically are specified by the systems manufacturer. Accordingly, component manufacturers and their distributors heretofore had to maintain stocks of different device varieties to satisfy customer requirements. Particularly with respect to expansion devices of the orifice piston variety, however, the need to maintain separate stocks of housing body components for accommodating the different varieties of pistons such as double headed and gasketed varieties represented a significant inventory expense. That is, it is known that body styles adapted for use with fluted pistons are not functional with pistons of a double headed construction, and vice versa.
Moreover, the forward end of the housing body typically is configured to receive a plurality of circuit tubes for connection to the associated coil. These tubes typically are brazed or otherwise welded to the coil, which then is supplied with the housing body as an integral unit. At least two separate stocks of these coil and body units therefore had to be maintained depending upon whether the particular application involved a device utilizing a gasketed or a double headed piston design.
In view of the foregoing, it is apparent that continued improvements in expansion devices for heat pump and other refrigeration circuits would be well-received by industry. A preferred orifice piston device construction would decrease inventory costs and the need to maintain separate body designs for different types of pistons while continuing to maintain proper operation of the refrigeration system.